The invention relates to a folding drum of a folder of a printing press.
Folders of printing presses serve to form folds on printed printing materials. In folders which are known from the prior art, a web-shaped printing material is usually guided first of all through a first longitudinal folding unit which is configured as a folding former in order thus to form a first longitudinal fold on the web-shaped printing material which is preferably not yet severed. Starting from the first longitudinal folding unit or from the folding former, the web-shaped printing material is guided in the direction of a crossfolding unit which comprises a cutting-knife cylinder, a folding-blade cylinder, a folding-jaw cylinder and optionally a gripper cylinder. In the region of the cutting-knife cylinder, copies are severed from the web-shaped printing material, which copies are moved in the direction of the folding-jaw cylinder with the aid of the folding-blade cylinder. The copies which are severed at the cutting-knife cylinder and are moved in the direction of the folding-jaw cylinder by the folding-blade cylinder are transferred to the folding-jaw cylinder with the formation of a first crossfold by the folding-blade cylinder. Further, second crossfolds can be formed between the folding-jaw cylinder and the gripper cylinder which interacts with the folding-jaw cylinder. Starting from the crossfolding unit, the copies which are provided thus with a longitudinal fold and with at least one crossfold pass into the region of a second longitudinal folding unit which usually comprises folding drums. Second longitudinal folds which extend parallel to the longitudinal fold which is formed in the first longitudinal folding unit are formed on the already pre-folded copies with the aid of the folding drums which in each case comprise a folding blade. A folding drum of this type is known from US Patent Application Publication No. 2005/0003943 A1.
The folding drum which is known from US 2005/0003943 A1 has two folding-drum side walls which lie opposite one another and on which journals act, it being possible for the folding drum to be mounted rotatably on a frame or framework via the journals. A folding-blade shaft or folding-blade spindle which is mounted rotatably via self-aligning roller bearings which are positioned in the region of the folding-drum side walls extends between the folding-drum side walls. The use of roller bearings of this type is necessary to absorb the forces which occur during operation of the folding drum, namely the process force, weight and centrifugal force. However, roller bearings require a relatively great minimum load which cannot be maintained, in particular, in the lower and medium rotational-speed ranges of the folding drum. In the event of sudden load drops, sliding movements between the rollers and the raceway of the roller bearings can be formed as a result of the mass moment of inertia and the pronounced reduction in the forces which act in the radial direction, which sliding movements can lead to increased bearing wear.